Method of scoring



United States Patent 3,495,434 METHOD OF SCORING Arthur A. Lavine, Torrance, Calif. (319 Palos Verdes BiWL, Apt. 212, Redondo Beach, Calif. 90277) Filed Oct. 9, I967, Ser. No. 673,715 Int. Cl. BZld 17/02, 31/00 US. Cl. 72-342 5 Claims ABSTRACT OF THE DISCLOSURE There is described herein a forming arrangement, in which a hollow member such as a tubular cylinder may be provided with an accurate and precise scoring pattern on the inside wall surfaces thereof. This is achieved by providing a tool member having in the external surface thereof the desired pattern for forming the grooves or other desired scoring that is to be provided on the inside of the hollow working member. The material from which the tool member is made has a different, and in this case, an appreciably smaller coetficient of linear thermal expansion than does the working member that is to be grooved. Further, the tool member must be of a hardness that is greater than the material forming the working member. Both the tool member and the working member may be heated so that there is just sufl-lcient clearance provided between the inside wall surfaces of the working member and the outside wall surface of the tool member. The tool member may then be inserted into the working member, and the units cooled to an ambient temperature. Since the tool member is harder than the working member, the raised groove-forming portions on the external surface thereof dig into and thereby score the predetermined pattern on the inside wall surface of the working member. The tool member and working member asembly may then be heated and, due to the larger coefiicient of expansion of the working member, at a sufficient temperature, it will have expanded sufliciently so that it may be removed from the tool member, and subsequently allowed to cool to its desired ambient temperature. The internal grooving thereon provides for a predetermined fragmentation pattern upon rupture of the working memher during subsequent utilization thereof.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the forming art and, more particularly, to improved methods for providing a predetermined scoring pattern upon preselected wall surfaces of a member.

Description of the prior art In many applications, for example, such as internal screw threads, providing a bomb or other member that preferably maintains an aerodynamically smooth external surface that is also designed to have a predetermined fragmentation pattern upon rupturing by means of explosives contained therein, or the like, it is desired to have a preselected scoring pattern on a wall. In bomb application the pattern may be a fracture including means on the internal wall surfaces of the working member so that, upon rupture, the predetermined fragmentation pattern will be obtained.

To the best of applicants knowledge, there has not generally been a satisfactory arrangement for generating such scoring upon the internal wall surfaces of a hollow member. In some applications, the member has been made in a split configuration so that, what will ultimately be an internal wall surface, is actually an external wall surface and readily available for machining; and then two matching pieces are assembled to form the working member. Such arrangements have not always proven to be satisfactory, since the desired homogeneity in the working member is destroyed by the requirement of its being originally fabricated in a split configuration.

SUMMARY OF THE INVENTION Accordingly, it is an object of applicants invention herein to provide an improved forming arrangement.

It is another object of applicants invention herein to provide an improved forming arrangement for generating a predetermined scoring pattern on a preselected wall surface of a working member.

It is yet another object of applicants invention herein to provide the structure and method for generating score lines on the internal wall surfaces of a hollow memher.

The above and other objects are achieved, according to one embodiment of applicants invention, by providing a tool member fabricated from a material having a comparatively low coefficient of thermal expansion and a comparatievly high hardness. The external surface of the tool member is provided with a negative pattern of the desired working member scoring pattern; and, for example, may comprise a series of raised ridges extending in predetermined directions to define a pattern. Such a tool member may be fabricated, for example, of chromium, having a 3.4 l0 inches per inch degree Fahreneit coefiicient of linear thermal expansion, of Brinell hardness of 600 to 1200, and a melting point of 3430 Fahrenheit.

The working member, which, for example, might be a bomb or some other Weapon arrangement, may be fabricated from steel, having a coefiicient of linear thermal expansion of 6.5 l0 inches per inch degree Fahrenheit, a Brinell hardness of less than 300, and a melting point on the order of 2800 Fahrenheit.

In one method, according to applicants invention herein, of providing the score pattern on internal wall surfaces it may be assumed that the working member is a tubular cylindrical member, and, correspondingly, the tool member is also cylindrical in shape. However, as noted, the working member is a tubular cylinder and the tool member is adapted to fit therein. The dimensions of the working member are such that, for example, at ambient temperature, the raised portions on the external surface of the tool member extend a preselected interference from the external surface thereof with the working member an amount equal to the depth desired for the scoring on the internal wall surfaces of the cylindrical Working member. Both the working member and the tool member may then be heated to a sufiicient temperature so that the maximum external diameter of the tool member is less than the internal diameter of the cylindrical working member. The tool member is then inserted inside the working member and the two members are cooled to ambient temperature. Upon cooling, since the working member shrinks a greater amount than the tool member, the ridges on the external surface of the tool member are forced into the internal wall surfaces of the working member to provide grooves therein in the corresponding desired pattern. This will occur since the tool member is fabricated from material harder than the working member.

After the pattern has been impressed into the internal wall surfaces of the working member, those units may be heated to a temperature sufficient so that there is again provided clearance between the largest external diameter of the tool member and the internal wall diameter of the working member; and the two units may be sep arated. The working member may then, for example, be further fashioned into an appropriate explosive-filled shell or any other desired member for subsequent utilization.

In other methods of forming the scoring on the internal surface of a cylindrical or hollow member, only the working cylinder is first heated to a temperature sufficient to provide clearance over the tool member, and the tool member is provided with an internal hollow passage through which a cooling material may be pumped. After the heated working member is placed over the tool member, it is allowed to cool to ambient temperature thereby impressing the score lines on the internal wall surfaces thereof. Then cooling material may be pumped through the hollow tool member, and, if desired, an electrical potential placed across the working member to increase its temperature. Therefore, there is a differential temperature established between the tool member and the working member, and this is increased until the working member may be removed from the tool member.

In other embodiments of applicants invention herein, the scoring pattern may be impressed on the external wall surface of a cylindrical working member by a tubular cylindrical tool member mounted concentrically therewith.

In still other embodiments of applicants invention herein, the desired scoring pattern may be provided by cooling one or both of the members before insertion of a temperature low enough to avoid the interference, and then heating to provide the scoring.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other embodiments of applicants invention may be more fully understood from the following detailed description taken together with the accompanying drawing wherein similar reference characters refer to similar elements throughout and in which:

FIGURE 1 illustrates a working member useful in the practice of applicants invention herein;

FIGURE 2 illlustrates a tool member useful in the practice of applicants invention herein;

FIGURE 3 is a sectional view along the line 33 of FIGURE 2;

FIGURE 4 illustrates another embodiment of applicants invention; and

FIGURE 5 illustrates another embodiment of applicants invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGURES 1, 2, and 3, there is shown the structure useful in the practice of one of the preferred r methods of applicants invention herein. As shown in FIGURE 1, there is a work piece, generally designated 10, in the form, in this example, of a hollow, tubular cylindrical member has a predetermined external wall surface 12, and an internal wall surface 16 defining the wall 14.

When the method of applicants invention herein has been utilized on the working member 10, as described below in greater detail, it may be filled with suitable explosives and detonation members and caps 18 and 20 installed thereon.

According to applicants invention herein, it is desired to provide internal grooving or scoring along the internal wall surfaces 16 of the tubular cylindrical working member 10, scoring pattern, such a pattern may be screw threads or, as shown on FIGURE 1, a scoring pattern to provide a predetermined fragmentation pattern upon detonation of any explosive contained in the passageway 24 defined by the internal wall 16. Since the fragmentation, in this em bodiment of applicants invention may be utilized as antipersonnel type weaponry, it is preferred that the working member 10 be fabricated from steel. As such, it will gen erally have a coefficient of linear thermal expansion on the order of 65x10" inches per inch degree Fahrenheit, a Brinell hardness of less 1211311 300, and a melting point on the ordergfi 2800? F. i I

In order to achieve the internal scoring to provide the predetermined fragmentation pattern, a tool member,

such as the tool member 26, shown in FIGURE 2, is fabricated from, for example, a material having a higher Brinell hardness and a lower coefficient of linear thermal expansion. Thus, the tool member 26 may be fabricated from, for example, chromium, having a coefficient of linear thermal expansion on the order of 3.4x 10* inches per inch degree Fahrenheit, and a Brinell hardness on the order of 600 to 1200. Such a material has a melting point on the order of 343G Fahrenheit.

If, for example, the working member 10 were fabricated from aluminum having a linear thermal coefiicient of expansion on the order of 13.3 10 inches per inch degree Fahrenheit, then the tool member 26 could be fabricated from steel having the above mentioned linear thermal coefiicient of expansion of 6.5 10- inches per inch de ree Fahrenheit. It is apparent that other combinations of materials may equally well be utilized as long as there is a difference in the thermal coefficients of expansion therebetween.

The external wall 28 of the generally cylindrical tool member 26, which, in this embodiment of applicants invention, is shown as a solid cylinder, is provided with a piurality of generally axially disposed V-shaped ridges 28 and a plurality of substantially circumferential V- shaped ridges 30. The ridges 28 and 30 are arranged to provide the predetermined scoring on the internal wall surface 16 of the working member 10, shown in FIG- URE 1. That is, the ridges 28 and 3f) define essentially a negative pattern of the desired fragmentation grooving.

In order to provide the predetermined scoring pattern on the surface 16 of the working member 10, as defined by the ridges 28 and 30, both the working member 10 and the tool member 26 may be heated to a sufficiently high temperature so that there is clearance between the minimum internal diameter of the passageway 24, and the maximum outer diameter of the ridges 30 or the ridges 28. The working member 10 is then slipped over the tool member 26 and both members are cooled to ambient temperatures. Since the coefficient of thermal expansion of the working member 10 is greater than the coefficient of thermal expansion of the tool member 26, differential contraction takes place and the working member 10 shrinks a greater amount than the tool member 26.

During such excessive shrinking, the ridges 28 and 30 of the tool member 26 dig into and provide grooves in the internal wall surfaces 16 of the tool member 10.

However, it is necessary to separate the two members so that the working member 10 may be separately utilized for its ultimate purpose. This separation is achieved, in this method of the practice of applicants invention herein, by heating both the tool member 26 and the working member 10 until a temperature is reached wherein there is once again provided clearance between the maximum diameter of the ridges 28 or the ridges 30, and the minimum inside diameter of the wall 26, defining the passageway 24 in the working member 10. When this temperature is reached, the working member 10 may be removed from the tool member 26 and allowed to cool to ambient temperature where it can be further utilized in any manner desired, such as in the anti-personnel explosive weaponry mentioned above.

Applicant has determined that in some applications, it may be desirable to avoid such extensive heating of the tool member 26 since it increases the probability of annealing, and, thus, softening the tool material and therefore rendering it useless for the purpose intended.

To achieve this result, in those applications where it is necessary, the structure shown in FIGURE 4 may be utilized. As shown thereon, there is a working member 46, but it may be similar to the workin member 10 shown in FIGURE 1, having internal wall surfaces 42 tgaon whih it is desired to provide a predetegmined soring to affectuate and open the fragmentation pattern upon bursting, and the internal walls 42 define a passageway 44 thereto. A tool member 46 is also provided and has a plurality of axially disposed V-shaped ridges 48 and a plurality of circumferentially disposed V-shaped ridges 50 thereon to provide the predetermined scoring pattern on the interior surface 42 of the working member 40. In this embodiment of applicants invention, however, the working member 40 is first increased to a temperature sufficiently great so that there is clearance between the minimum dimension of the internal wall surface 42 thereof and the maximum dimension of the ridges 48 or 50 on the tool member 46. Thus, the tool member 46 stays subs antially at ambient temperature.

The Working member 40 may then be inserted over the tool member 46, and the working member 40 may then be cooled by any desired means to provide a shrink fit over the tool member 46, and thus, due to the hardness of the tool member 46 compared to the Working member 40, the V-shaped ridges 48 and 50 dig into the internal wall surfaces 42 of the working member 40 to provide the desired grooving for ultimate fragmentation pattern control.

In order to remove the working member 40 from the tool member 46, in this embodiment of applicants invention, the entire assembly of both the working member 40 and tool member 46 may be heated to a comparatively low temperature, such as a few hundred degrees Fahrenheit above ambient, which then provides a small clearance or ulage space between the internal wall surface 42 of the working member 40 and the external surface of the tool member 46. An electrically insulating material may be pumped into this ulage space and an electrical potential, such as from source of electrical energy 52, may be applied to the working member 40 through switch 54. Due to the resistivity of the working member 40, it increases in temperature and the electric current applied thereto is continued until such time as there is sufiicient clearance to allow removal of the working member 40. The insulation pumped into the ulage space allows electrical isolation of the tool member 46 from the working member 40.

In order to further aid in the differential expansion 50 that the minimum absolute temperature may be utilized in the working member 40, applicant may desire to pump a coolant such as ice brine in the direction indicated by the arrow 56 to an aperture 58 substantially axially disposed in the tool member 46 and the ice brine exits from the aperture 58 in the direction indicated by the arrow 60. The cooling brine helps maintain the entire tool member 46 at a comparatively low temperature so as to aid in the temperature differential actually obtained in the practice of applicants invention by this method.

Alternatively, instead of providing an electrically insulating material in the clearance spaces between the working member 40 and the tool member 46, it may be desired to apply an electric current to both the tool member 46 and the working member 40, as indicated by the electrical connections shown as 61 and 62; and, therefore, heat both the tool member and the working member 40. This, of course, will heat each of the tool member 46 and working member 40; and due to the different coefficients of linear thermal expansion, the working member 40 will increase in size faster than the tool member 46 to ultimately provide a clearance therebetween at a predetermined temperature.

In yet other embodiments of applicants invention it may be desired to provide a preselected scoring pattern on the external wall of a cylindrical member. The structure for practicing this method of applicants invention is illustrated in FIGURE 5. As shown thereon, there is a tool member 80 that is in a generally tubular cylindrical shape. That is, in this embodiment of applicants invention, the tool member 80 has an external Wall 82 and an internal wall 84. The internal wall 84 is provided with a screw thread 86 having a desired pitch and thread depth. In this embodiment of applicants invention it may be desired to provide the screw thread on the external wall surface 88 of a generally cylindrical working member 90. Thus, for example, the tool member may be fabricated from chromium and the working member 90 may be fabricated from steel. Alternatively, of course, as noted above, the tool member 80 may be fabricated from steel and the working member 90 may be fabricated from aluminum.

In general, in the practice of the various methods of applicants invention herein, it can be seen that it is necessary that the tool member be harder than the working member and, further, that there be a different thermal expansion therebetween.

In the structure of applicants invention shown on 5 herein and with the working member 90 fabricated from steel and with the tool member 80 fabricated from chromium, it is necessary that a size difference between the external diameter of the working member 90 and the internal diameter of the tool member 80. Accordingly, since the steel has a greater coefficient of thermal expansion than the chromium, the cylindrical working member 90 may be cooled in a preselected temperature and, if necessary, the tool member 80 increased in temperature so that the working member 90 may be inserted into the passageway 92 defined by the internal wall surface 84 of the tool member 80. When this insertion has been completed, the assembly may be heated to a sulficient value so that the working member 90 increases in diameter sufficiently to provide the forming of the screw threads 94- thereon by the screw threads 86 in the tool member 80.

It is apparent that this method of practicing applicants invention may be utilized in many diverse applications wherein it is necessary to cool one of the tool members or the working member in order to provide sufficient clearance for insertion of the one in the other depending upon which is the tubular member and which is the cylindrical member.

For the arrangement shown in FIGURE 5, when it is desired to remove the working member 90 from the tool member 80, it is necessary to repeat the process and cool the assembly. Since the coefficient of thermal expansion of the working member 90 is greater than that of the tool member 80 the Working member 0 shrinks a greater amount than the tool member 80 and When the unit has been cooled to a sufficient temperature, the working member 90 may be removed.

In the practice of applicants invention herein it can be seen that there are several possible combinations and variations of the various parameters associated with applicants invention. For example, the working member may be either tubular or cylindrical and, conversely, the tool member may be either cylindrical or tubular respectively. Further, either the working member may have a larger coefficient of thermal expansion than the tool member or it may have a smaller coefficient of thermal expansion than the tool member. In a rare situation the coefficients of thermal expansion may be the same in which case special provisions must be included so that there is provided a temperature differential sufficient to allow the insertion of one of the members in the other and then either differential heating of the tubular member so that it expands while the cylindrical member remains at the forming temperature or else differential cooling of the cylindrical member so that it shrinks while the tubular member remains at the forming temperature. In the other situation the working member may be cylindrical and, correspondingly, the tool member may be tubular and in this case also the working member may have a larger coefficient of thermal expansion or a small coefiicient of thermal expansion for the tool member. Therefore, in general, there will be a difference in thermal coefficient of expansion between the Working member and tool member.

In all embodiments of applicants invention it is necessary, of course, that the tool member be harder than the working member.

With the exception of the situation described above wherein the thermal coefficients of expansion are the same, the thermal coefficients of expansion will generally be different and the following situations may occur:

(1) If the working member is tubular and the tool member is cylindrical and it is desired to form the scoring pattern on the internal surface of the tubular working member, then in the first case if the thermal coefficient of expansion of the working member is larger than the thermal coefficient of expansion of the cylindrical member, then to insert the tool member in the working member is preferable to heat the working member and to form the scoring pattern, it is preferable to cool the working member and to remove the tool member from the working member it is desirable to heat the assembly. If the tubular working member has a smaller coefficient of thermal expansion than the cylindrical tool member, then it is preferred to cool the cylindrical tool member to insert the tool member in the working member and then heat the cylindrical tool member to provide the forming of the scoring pattern. To remove the working member from the tool member it is preferable to cool the cylindrical tool member.

If the working member is cylindrical and the tool member is tubular and it is desired to provide the predetermined scoring pattern on the external surface of the cylindrical working member and if the thermal coefiicient of expansion of the cylindrical working member is larger than the thermal coefficient of expansion of the tubular tool member, it is preferable to cool the cylindrical working member to insert the cylindrical working member in the tubular tool member, then heat the cylindrical working member to provide the forming and then cool the cylindrical working member to remove the cylindrical working member from the tubular tool member. If the thermal coefficient of expansion of the cylindrical working member is smaller than the thermal coefficient of expansion of the tubular tool member then it is preferable to heat the tubular tool member to insert the cylindrical working member in the tubular tool member, cool the tubular tool member to form the preselected scoring pattern and then heat the tubular tool member to remove the cylindrical working member from the tubular tool member.

In all of the above combinations of embodiments of applicants invention prior to inserting the cylindrical member in the tubular member it may be advantageous to increase the temperature differential between the cylindrical and the tubular member and then during forming operation the temperatures of the tool members may move in the same direction. That is, they may both increase or decrease depending upon the characteristics as defined above. During the removal operation the temperature of both the tubular member and cylindrical member may also move in the same direction in accordance with the above.

This concludes the description of applicants invention of the improved forming method. From the above, it can be seen that applicant has provided a unique and desirable method for providing scoring or grooving on a member. Those skilled in the art may find many variations and adaptations thereof and the appended claims are intended to cover all such variations and adaptations falling within the true scope and spirit of applicants invention.

While applicant has described his invention as utilized in cylindrical working and tool members, it is, of course, not so limited. That is, as noted above, as long as there is at least one hollow member having a passageway therethrough and another member positionable in the hollow member, which may be termed an inner member, the invention may be practised.

Such diverse geometrical shapes as spheres, for scoring on the external surface, or cones, elliptical cylinders, boat tails or the line, for scoring an external or internal surface, may be utilized in the practice of applicants invention herein.

The tubular member 10 in FIGURE 1, 40 in FIG- URE 4 and in FIGURE 5 may be considered the hollow member, whether it is the working member or the tool member may be termed the hollow member. Similarly, the cylindrical member 26 in FIGURE 2, 46 in FIGURE 4 and in FIGURE 5, whether it is the working member or tool member, may be termed the inner member and is positionable within the passageway of the hollow member.

I claim:

1. A method of providing a preselected scoring pattern on a working member by utilizing a tool member having a hardness greater than the working member and in which the thermal linear coeflicients of expansion of the working member and the tool member are different and one of said working member and said tool member comprising a hollow member and the other of said working member and said tool member comprising an inner member and one of the internal walls of the hollow member and the external walls of the inner member having ridges thereon for forming in the other of said internal walls of said hollow member and external walls of said inner member a predetermined scoring pattern, comprising the steps of:

providing a temperature differential between the temperature of the working member and the temperature of the tool member;

inserting the inner member in the hollow member;

changing the temperature of one of said working member and said tool member to decrease the separation therebetween to force the ridges into the adjacent wall surface;

providing a temperature differential between the working member and the tool member; and

removing the hollow member from the inner member.

2. The method defined in claim 1 wherein said working member comprises the hollow member and the inner member comprises the tool member and the tool member has a plurality of ridges on the external surface thereof for forming a predetermined scoring pattern on the internal surfaces of the hollow working member and the thermal coefficient of expansion of the working member is larger than the thermal coefficient of expansion of the tool member and in which:

the working member is heated prior to the insertion of the tool member therein;

the working member is cooled to provide the preselected scoring pattern on the internal wall surfaces thereof;

and the working member is heated to allow removal of the hollow member therefrom.

3. The method defined in claim 1 wherein the working member is hollow and the tool member is the inner member and the working member has a smaller coefficient of thermal expansion than the tool member and the tool member has a plurality of ridges on the external surface thereof for forming a predetermined scoring pattern on the internal surface of the hollow working member and in which:

the tool member is cooled relative to the temperature of the working member to allow insertion of the tool member in the working member;

the tool member is heated to provide the forming of the preselected scoring pattern on the internal wall surfaces of the working member;

and the tool member is cooled to allow removal of the cylindrical tool member from the tubular working member.

4. The method defined in claim 1 wherein the working member is the inner member and the tool member is the hollow member and the tool member has a plurality of ridges on the internal surface thereof for providing a predetermined scoring member and the inner working member has a larger linear coefficient of thermal expansion than the hollow tool member, and in which: the inner working member is cooled relative to the temperature of the hollow tool member to allow insertion of the inner Working member into the hollow tool member;

the inner working member is heated to provide forming of the preselected scoring pattern on the external surface thereof;

and the inner working member is cooled relative to the temperature of the hollow tool member to allow removal of the inner working member therefrom.

5. The method defined in claim 1 wherein the working member is the inner member and the tool member is hollow and the tool member has a plurality of ridges on the internal surface thereof for providing a predetermined scoring pattern on the external wall surface of the inner working member and the inner working member has a smaller linear thermal coeflicient of expansion than the hollow tool member and in which:

the hollow tool member is heated relative to the temperature of the inner working member to allow insertion of the inner working member in the hollow tool member;

the hollow tool member is cooled to form the preselected scoring pattern on the external wall surfaces of the inner working member;

and the hollow tool member is heated relative to the temperature of the inner working member to allow removal of the inner working member from the hollow tool member.

References Cited UNITED STATES PATENTS 1/1967 Stuart 72-342' 5/1968 Van Hartesveldt 72-342 US. Cl. X.R. 

